How side airbags work
When fully inflated, the side airbags reduce the risk of chest injury.

Fig. 184 Side airbags deployed
In certain side collisions, the side airbag deploys on the side exposed to the impact => fig. 184.
Some accidents may cause the front airbags as well as the side and curtain airbags to deploy.
When the system is activated, the airbag fills with gas.
The airbags inflate in a fraction of a second, at very high speed, to provide additional protection in an accident. A fine dust is released when the airbag deploys. This is completely normal and should not be mistaken for a fire in the vehicle.
When the occupants are thrown into the fully deployed airbag, their movement is cushioned and the risk of chest, abdomen and pelvis injury on the door side is reduced.
Test yourself
A quick Audi A4 quiz: every answer comes with an explanation and a link to the manual page.